Which phone operating system is best?

Hello friends, Good afternoon. Today morning i was drinking coffee and i saw my son using I-phone. Suddenly a question raised in my mind that there many operating systems available in the market, people usually get confused about selecting best operating system as every operating system has some pros and cones. Presently I am using android OS and I am satisfied with the system performance. so it is very interesting to know, which operating system is more popular among below mentioned options.